Methods and systems of cooling process plant water

ABSTRACT

The present disclosure provides methods and system for the cooling of process plant water. A system can include a first heat exchanger for exchanging heat between a first process water stream and a refrigerant; a multiphase pump, coupled to the first heat exchanger, to increase the pressure of the refrigerant; a second heat exchanger, coupled to the multiphase pump and the first heat exchanger, for exchanging heat between a second process water stream and the refrigerant; a first expansion valve, coupled to the second heat exchanger, for lowering the temperature of the refrigerant; a vapor-liquid separator, coupled to the first expansion valve and the multiphase pump, for separating the liquid and vapor phases of the refrigerant; and a second expansion valve, coupled to the vapor-liquid separator and the first heat exchanger, for lowering the temperature of the liquid phase of the refrigerant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/295,797, filed Feb. 16, 2016, which is herebyincorporated by reference in its entirety.

BACKGROUND

This disclosure relates to methods and systems for cooling process plantwater.

Petrochemical processing plants, such as those involved in theprocessing of natural gas and olefins and the generation of syngas, caninclude refrigeration systems that use water-based coolants, alsoreferred to as process plant water, for cooling components of theprocessing plant. For example, certain water-based cooling systems canbe used to remove heat from reactions performed in a processing plantand for the separation of substances within hydrocarbon mixtures for usein a processing plant. Water-based cooling systems can also be used forthe condensation of hydrocarbon gas streams.

Refrigeration methods and systems in the petrochemical industry can usea series of two-stage compressors, flash drums, liquid pumps, coolingtowers and heat exchangers, which can lead to high capital and operatingcosts. Therefore, there remains a need in the art for more efficient andcost-effective methods of cooling process water.

SUMMARY

The disclosed subject matter provides methods for cooling process plantwater including exchanging heat between a first process water stream anda liquid refrigerant within a first heat exchanger to lower thetemperature of the process water stream. In certain embodiments, therefrigerant is partially vaporized upon the exchange of heat with thefirst process water stream to generate a partially vaporized refrigeranthaving a vapor phase and a liquid phase. The method can includeincreasing the pressure of the partially vaporized refrigerant andtransferring at least a portion of the refrigerant to a second heatexchanger.

In certain embodiments, the method includes exchanging heat between asecond process water stream and the partially vaporized refrigerantwithin the second heat exchanger to decrease the temperature of therefrigerant. The method can include lowering the pressure and/ortemperature of the partially vaporized refrigerant portion andtransferring the partially vaporized refrigerant portion to avapor-liquid separator to separate the liquid phase from the vapor phasethereof, thereby generating a liquid refrigerant. The method can furtherinclude lowering the temperature of the liquid refrigerant andtransferring at least a portion of the refrigerant to the first heatexchanger to exchange heat with the first process water stream. Themethod can include transferring the cooled process water to one or moreprocess plants. The pressure of the partially vaporized refrigerant canbe increased in a multiphase pump.

In certain embodiments, the vapor-liquid separator can be a flash drum.In certain embodiments, the liquid refrigerant includes a refrigerantthat has a viscosity greater than or equal to about 0.1 cP at atemperature of about 0° C. In certain embodiments, the liquidrefrigerant includes a refrigerant that has a boiling point temperaturefrom about −10° C. to about −50° C. The liquid refrigerant can be R134A,R404A, R407C, R125 and R410A, and the partially vaporized refrigerantcan have a vapor phase of about 30% to about 50%.

The disclosed subject matter also provides techniques for coolingprocess plant water that includes exchanging heat between a firstprocess water stream and a liquid refrigerant to lower the temperatureof the process water stream, thereby generating a partially vaporizedrefrigerant. An example method can further include increasing thepressure and/or temperature of the partially vaporized refrigerant togenerate a pressurized partially vaporized refrigerant. The method caninclude exchanging heat between a second process water stream and thepressurized refrigerant to increase the temperature of the secondprocess water stream and/or lower the temperature of the pressurizedpartially vaporized refrigerant. The method can include lowering thepressure and/or temperature of the pressurized partially vaporizedrefrigerant and separating out at least a portion of a liquid phase fromthe partially vaporized refrigerant to generate a liquid refrigerant,and lowering the temperature of the liquid refrigerant to generate arefrigerant suitable for exchanging heat with the first process waterstream.

The disclosed subject matter further provides methods for coolingprocess plant water that includes exchanging heat between a firstprocess water stream and a liquid refrigerant within a first heatexchanger to lower the temperature of the process water stream, therebypartially vaporizing the refrigerant upon the exchange of heat with thefirst process water stream. An example method can further includetransferring the first process water from the first heat exchanger toone or more process plants, and transferring the partially vaporizedrefrigerant from the first heat exchanger to a multiphase pump toincrease the pressure of the partially vaporized refrigerant. The methodcan include transferring the partially vaporized refrigerant from themultiphase pump to a second heat exchanger. The method can furtherinclude exchanging heat between a second process water stream and thepartially vaporized refrigerant within the second heat exchanger tolower the pressure and/or temperature of the refrigerant. The method caninclude transferring the second process water stream from the secondheat exchanger to become the first process water stream entering thefirst heat exchanger. The method can include transferring the partiallyvaporized refrigerant from the second heat exchanger to a firstexpansion valve to lower the pressure and/or temperature of therefrigerant.

The method can include transferring the partially vaporized refrigerantfrom the first expansion valve to a vapor-liquid separator to separatethe liquid phase from the vapor phase thereof, thereby generating aliquid refrigerant. In certain embodiments, the method can includetransferring the liquid refrigerant from the vapor-liquid separator to asecond expansion valve to lower the temperature of the liquidrefrigerant, and transferring the refrigerant from the second expansionvalve to the first heat exchanger to exchange heat with the firstprocess water stream.

The disclosed subject matter further provides methods for coolingprocess plant water that includes exchanging heat between a firstprocess water stream and a liquid refrigerant within a first heatexchanger to lower the temperature of the process water stream. Therefrigerant can be partially vaporized upon the exchange of heat withthe first process water stream. The method can include transferring thepartially vaporized refrigerant from the first heat exchanger to avapor-liquid separator to separate the vapor phase from the liquid phaseof the refrigerant. The method can include transferring the vapor phaseof the refrigerant to a gas compressor for the compression of therefrigerant. The method can include combining the compressed vapor phaseof the refrigerant with the liquid phase of the refrigerant to generatea pressurized partially vaporized refrigerant, and exchanging heatbetween a second process water stream and the refrigerant within asecond heat exchanger to lower the temperature of the refrigerant.

In certain embodiments, the method can include transferring therefrigerant from the second heat exchanger to a first expansion valve tolower the pressure and/or temperature of the refrigerant. The method canfurther include transferring the refrigerant from the first expansionvalve to a second vapor-liquid separator to separate the vapor phasefrom the liquid phase of the refrigerant. In certain embodiments, themethod can include transferring the liquid phase of the refrigerant fromthe second vapor-liquid separator to a second expansion valve to lowerthe temperature of the liquid refrigerant and transferring therefrigerant from the second expansion valve to the first heat exchangerto exchange heat with the first process water stream. The refrigerantcan be partially vaporized to have a liquid fraction of about 98%. Incertain embodiments, the method can further include transferring thevapor phase of the refrigerant from the second vapor-liquid separator tothe gas compressor.

The disclosed subject matter also provides systems for cooling processplant water that includes a first heat exchanger for exchanging heatbetween a first process water stream and a refrigerant. In certainembodiments, the system can further include a multiphase pump, coupledto the first heat exchanger, to increase the pressure of therefrigerant. In certain embodiments, the system can include a secondheat exchanger, coupled to the multiphase pump and the first heatexchanger, for exchanging heat between a second process water stream andthe refrigerant. The system can include a first expansion valve, coupledto the second heat exchanger, for lowering the temperature of therefrigerant. The system can further include a vapor-liquid separator,coupled to the first expansion valve and the multiphase pump, forseparating the liquid and vapor phases of the refrigerant, and a secondexpansion valve, coupled to the vapor-liquid separator and the firstheat exchanger, for lowering the temperature of the liquid phase of therefrigerant. The vapor-liquid separator can be flash drum.

In certain embodiments, a system for cooling process plant waterincludes a first heat exchanger for exchanging heat between a firstprocess water stream and a refrigerant. The system can include a firstvapor-liquid separator, coupled to the first heat exchanger, to separatethe vapor phase from the liquid phase of the refrigerant. The system canfurther include a pump, coupled to the first vapor-liquid separator, fortransferring at least a portion of the liquid phase of the refrigerant.The system can include a gas compressor, coupled to the firstvapor-liquid separator, for increasing the pressure of the vapor phaseof the refrigerant. It can also include a transfer line, coupled to thegas compressor and the pump, for combining the vapor phase of therefrigerant and the compressed liquid phase of the refrigerant, therebygenerating a partially vaporized refrigerant. The system can include asecond heat exchanger, coupled to the transfer line and the first heatexchanger, for exchanging heat between a second process water stream andthe refrigerant. The system can include a first expansion valve, coupledto the second heat exchanger, for lowering the temperature of therefrigerant, and a second vapor-liquid separator, coupled to the firstexpansion valve and the gas compressor, for separating the liquid andvapor phases of the refrigerant. The system can include a secondexpansion valve, coupled to the second vapor-liquid separator and thefirst heat exchanger, for lowering the temperature of the liquid phaseof the refrigerant and transferring the refrigerant to the first heatexchanger. In certain embodiments, the refrigerant being transferredfrom the second expansion valve to the first heat exchanger has vaporfraction of about 2% and/or a liquid fraction of about 98%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a method for cooling process plant water according to oneexemplary embodiment of the disclosed subject matter.

FIG. 2 depicts a method for cooling process plant water according to oneexemplary embodiment of the disclosed subject matter.

FIG. 3 depicts a system for cooling process plant water according to oneexemplary embodiment of the disclosed subject matter.

FIG. 4 depicts a system for cooling process plant water according to oneexemplary embodiment of the disclosed subject matter.

DETAILED DESCRIPTION

The disclosed subject matter provides techniques for cooling processplant water. In particular non-limiting embodiments, the presentlydisclosed subject matter provides closed-loop methods and systems forcooling process plant water. In certain embodiments, the methods and/orsystems of the present disclosure do not include a heat sink, e.g., acooling tower.

Water-based coolant, i.e., process plant water, can be used to coolindustrial plants such as petrochemical plants (also referred to hereinas process plants and processing plants). The process plant water caninclude water from any source, such as but not limited, potable water,demineralized water, ocean water, sea water, ground water, stream wateror river water. In certain embodiments, the process plant water can havea pH of about 7 to about 8 and/or an amount less than or equal to about0.15 mg/kg of dissolved solids. In certain embodiments, such processplant water can be used for the condensation of hydrocarbon gas streams,for the separation of substances within a mixture for use in the processplant and/or for the removal of heat from chemical reactions within theprocess plant.

For the purpose of illustration and not limitation, FIGS. 1 and 2 areschematic representations of methods according to non-limitingembodiments of the disclosed subject matter. In certain embodiments, themethod 100 or 200 includes exchanging heat between a first process waterstream and a liquid refrigerant to lower the temperature of, i.e., cool,the first process water stream 101 or 201. Heat exchange between thefirst process water stream and refrigerant can occur within a first heatexchanger to form a cooled first process water stream.

In certain embodiments, prior to exchanging heat with the refrigerant,the first process water stream can have a temperature from about 35° C.to about 40° C. In certain embodiments, the temperature of the firstprocess water stream prior to heat exchange with the refrigerant can beabout 38° C. In certain embodiments, after exchanging heat with therefrigerant, the temperature of the first process water stream can befrom about 24° C. to about 26° C. In certain embodiments, thetemperature of the first process water stream can be lowered to atemperature of about 25° C. after exchanging heat with the refrigerant.

As used herein, the term “about” or “approximately” means within anacceptable error range for the particular value as determined by one ofordinary skill in the art, which will depend in part on how the value ismeasured or determined, i.e., the limitations of the measurement system.For example, “about” can mean a range of up to 20%, up to 10%, up to 5%and/or up to 1% of a given value.

The liquid refrigerant for use in the disclosed subject matter can beany refrigerant that has a viscosity equal to or greater than about 0.1centipoise (cP). In certain embodiments, the refrigerant has a viscosityfrom about 0.1 cP to about 1.0 cP or from about 0.1 cP to about 0.5 cP.For example, and not by way of example, the refrigerant can have aviscosity from about 0.1 cP to about 0.45 cP, from about 0.1 cP to about0.4 cP, from about 0.1 cP to about 0.35 cP, from about 0.1 cP to about0.3 cP, from about 0.1 cP to about 0.25 cP, from about 0.1 cP to about0.2 cP, from about 0.1 cP to about 0.15 cP, from about 0.15 cP to about0.50 cP, from about 0.20 cP to about 0.50 cP, from about 0.25 cP toabout 0.50 cP, from about 0.30 cP to about 0.50 cP, from about 0.35 cPto about 0.50 cP, from about 0.40 cP to about 0.50 cP or from about 0.45cP to about 0.5 cP. In certain embodiments, the viscosity of therefrigerant is measured at 0° C.

The refrigerant for use in the disclosed subject matter can have aboiling point temperature of about −10° C. to about −50° C. For example,the refrigerant can have a boiling point temperature of about −10° C. toabout −45° C., about −10° C. to about −40° C., about −10° C. to about−35° C., about −10° C. to about −30° C., about −10° C. to about −25° C.,about −10° C. to about −20° C., about −10° C. to about −15° C., about−15° C. to about −50° C., about −20° C. to about −50° C., about −25° C.to about −50° C., about −30° C. to about −50° C., about −35° C. to about−50° C., about −40° C. to about −50° C. or about −45° C. to about −50°C. Such low boiling point temperatures can allow the refrigerant toevaporate easily and exchange heat rapidly with the process waterstream. Non-limiting examples of refrigerants suitable for use in thedisclosed subject matter include hydrocarbon-based refrigerants, R134A,R404A, R407C, R125 and R410A.

In certain embodiments, prior to exchanging heat with the first processwater stream, the temperature of the refrigerant can be from about 5° C.to about 10° C., e.g., about 9° C. In certain embodiments, afterexchanging heat with the first process water stream, the temperature ofthe refrigerant can be from about 7° C. to about 20° C.

In certain embodiments, the refrigerant is at least partially vaporizedupon the exchange of heat with the first process water stream.“Partially vaporized,” as used herein, can mean that more than about10%, more than about 20%, more than about 30%, more than about 35%, morethan about 40%, more than about 45%, more than about 50% or more thanabout 55% of the refrigerant is vaporized (i.e., is in the vapor phase).In certain embodiments, “partially vaporized” can mean that about 30% toabout 40% of the refrigerant is vaporized following the exchanging ofheat between the refrigerant and the first process water stream. Incertain embodiments, about 40% of the refrigerant is vaporized followingthe exchanging of heat between the refrigerant and the first processwater stream.

The method 100 or 200 can further include transferring the cooled firstprocess water stream, e.g., from the first heat exchanger, to one ormore process plants 102 or 202. The process plant can be any plant thatuses process water for cooling the one or more reactors and/or gasstreams of the process plant. For example, the cooled process water canbe transferred to a process plant that produces aromatics, specialitychemicals, olefins, methanol, syngas, etc.

In certain embodiments, and with reference to FIG. 1, the method 100 canfurther include increasing the pressure of the partially vaporizedrefrigerant 103 to, for example, generate a pressurized partiallyvaporized refrigerant. In certain embodiments, the pressure of thepartially vaporized refrigerant can be increased within a multiphasepump, e.g., by transferring the partially vaporized refrigerant from thefirst heat exchanger to the multiphase pump. For example, and not by wayof limitation, at least a portion of the partially vaporized refrigerantis transferred from the first heat exchanger to the multiphase pump. Asused herein, “at least a portion” can refer to an amount greater thanabout 40%, greater than about 50%, greater than about 60%, greater thanabout 70%, greater than about 80%, greater than about 90%, greater thanabout 95% or greater than about 99%.

In certain embodiments, the pressure of the partially vaporizedrefrigerant can be increased to a pressure of about 5 bar to about 15bar, e.g., to about 14 bar. The heat generated by the multiphase pumpcan increase the temperature and/or increase the percentage of the vaporphase of the partially vaporized refrigerant. After pressurization, therefrigerant can have a vapor fraction of about 55% to about 60%. Incertain embodiments, the partially vaporized refrigerant can have avapor fraction of about 55% after the increase in pressure, e.g., withinand/or exiting the multiphase pump. The temperature of the partiallyvaporized refrigerant can increase to a temperature of about 50° C. toabout 55° C. In certain embodiments, the temperature of the pressurizedpartially vaporized refrigerant can increase to a temperature of about52° C.

Alternatively or additionally, and as depicted in FIG. 2, the method ofthe disclosed subject matter 200 can include separating the liquid phasefrom the vapor phase of the partially vaporized refrigerant 203. Incertain embodiments, at least a portion of the liquid phase of therefrigerant is separated from the vapor phase of the refrigerant. Theseparation of the liquid phase from the vapor phase of the refrigerantcan occur by transferring the partially vaporized refrigerant from thefirst expansion valve to a vapor-liquid separator, e.g., a flash drum.In a vapor-liquid separator, a stream of a liquid/vapor mixture, e.g., amultiphasic refrigerant, can be fed through a throttling valve at theentry point (feed inlet) into the vapor-liquid separator, causing rapidreduction in pressure and partial vaporization (flashing) of the liquidin the stream. Gas can be removed from a gas outlet (vapor outlet) atthe top of the vapor-liquid separator while liquid can be removed from aliquid outlet at the bottom of the vapor-liquid separator. The separatedvapor phase of the refrigerant can undergo compression, e.g., within agas compressor, and can be combined with the separated liquid phase togenerate a partially vaporized refrigerant 204, e.g., a pressurizedpartially vaporized refrigerant. The compressed vapor can have atemperature of about 57° C. and a pressure of about 14 bar followingcompression. In certain embodiments, the liquid refrigerant exiting theliquid pump can have a temperature of about 9° C. and a pressure ofabout 14 bar. In certain embodiments, the partially vaporizedrefrigerant obtained after the mixing of the compressed vaporrefrigerant and the liquid refrigerant exiting the liquid pump can havea temperature of about 52° C. and a pressure of about 14 bar.

In certain embodiments, the method 100 or 200 can further includeexchanging heat between a second process water stream and thepressurized partially vaporized refrigerant 104 or 205. The heatexchange between the second process water stream and refrigerant canoccur within a second heat exchanger. The second process water streamcan be a process water stream exiting from a process plant, as depictedin FIGS. 3 and 4. The second process water stream can have a temperatureof about 30° C. to about 33° C., e.g., about 31° C., prior to exchangingheat with the refrigerant. After exchanging heat with the refrigerant,the second process water stream can have a temperature of about 38° C.to about 42° C., e.g., about 38° C. The refrigerant can have atemperature of about outlet temperature of about 50° C. to about 52° C.,e.g., about 51° C., and/or have an outlet vapor phase of about 40% toabout 55%, e.g., about 40%, after exchanging heat with the secondprocess water stream. The refrigerant can have a vapor fraction of about60% upon entrance into the second heat exchanger. The method can includecombining the second process water stream, after heat exchange with therefrigerant, with the first process water stream, e.g., prior toentrance into the first heat exchanger. The second process water streamcan become the first process water stream, as depicted in FIGS. 3 and 4,to generate a closed process water loop and allow recycling of thesecond process water stream to the process plant.

In certain embodiments, the method 100 or 200 can further includelowering the pressure and/or temperature of the pressurized partiallyvaporized refrigerant 105 or 206. In certain embodiments, at least aportion of the pressurized partially vaporized refrigerant can betransferred from the second heat exchanger to a first expansion valve tolower the pressure and/or temperature of the refrigerant. For example,and not by way of limitation, the pressure of the refrigerant withinand/or exiting the first expansion valve can be about 4 bar to about 5bar, e.g., about 4 bar. Alternatively or additionally, the temperatureof the refrigerant within and/or exiting the first expansion valve canbe about 10° C. to about 13° C., e.g., about 11° C. The vapor fractionof the refrigerant can increase to about 45% to about 75% of therefrigerant, e.g., 45%.

The method 100 or 200 can further include separating the liquid phasefrom the vapor phase of the refrigerant 106 or 207. In certainembodiments, at least a portion of the liquid phase of the refrigerantis separated from the vapor phase of the refrigerant to generate aliquid refrigerant. In certain embodiments, the separation of the vaporphase from the liquid phase of the refrigerant can occur by transferringthe refrigerant from the first expansion valve to a vapor-liquidseparator. With reference to FIG. 1, the method 100 can includetransferring the vapor phase of the refrigerant from the vapor-liquidseparator to the multiphase pump. Alternatively, and in reference toFIG. 2, the method 200 can include transferring the vapor phase of therefrigerant from the vapor-liquid separator to the gas compressor.

The method 100 or 200 can include lowering the temperature of the liquidphase of the refrigerant 107 or 208, e.g., to form a cooled liquidrefrigerant. Such temperature lowering can include transferring at leasta portion of the liquid phase of the refrigerant from the vapor-liquidseparator to a second expansion valve. The liquid phase of therefrigerant within or exiting the second expansion valve can includeabout 1% to about 2%, e.g., 1.5%, of vapor. The temperature of theliquid refrigerant can be lowered to a temperature of about 8° C. toabout 10° C., e.g., about 9° C. In certain embodiments, the method 100or 200 can further include transferring the cooled refrigerant to thefirst heat exchanger for the cooling of the first process stream water,e.g., to generate a closed-loop method for cooling process plant water.

The disclosed subject matter further provides systems for the cooling ofprocess plant water. For example, FIGS. 3 and 4 are schematicrepresentations of systems according to non-limiting embodiments of thedisclosed subject matter. In certain embodiments, the system 300 or 400can include a first heat exchanger 301 or 401. Heat exchangers can beused to transfer heat from one medium or phase to another. For example,and not by way of limitation, the first heat exchanger 301 or 401 of thedisclosed subject matter can be used for exchanging heat between a firstprocess water stream and the liquid refrigerant.

The heat exchangers can be of various designs known in the art. Incertain embodiments, the heat exchangers can be double pipe exchangers,and can include a bundle of tubes housed in a shell, such that fluids tobe warmed or cooled within the heat exchanger flow through the shelland/or bundle of tubes. In certain embodiments, the heat exchangers caninclude corrosion-resistant materials, an alloy, e.g., steel or carbonsteel, or brazed aluminum.

The first heat exchanger 301 or 401 can be coupled to one or moreprocess plant systems 302 or 402. Non-limiting examples of process plantsystems are disclosed above. “Coupled” as used herein refers to theconnection of a system component to another system component by anymeans known in the art. The type of coupling used to connect two or moresystem components can depend on the scale and operability of the system.For example, coupling of two or more components of a system can includeone or more joints, valves, transfer lines or sealing elements.Non-limiting examples of joints include threaded joints, solderedjoints, welded joints, compression joints and mechanical joints.Non-limiting examples of valves include gate valves, globe valves, ballvalves, butterfly valves and check valves.

In certain embodiments, the system 300 can further include a multiphasepump 303. The multiphase pump for use in the present disclosure can beused to pump a medium that includes multiple phases, e.g., gas andliquid, to a higher pressure. The multiphase pump 303 can be used toincrease the pressure of the refrigerant and can be coupled to the firstheat exchanger 301. Alternatively and/or additionally, and in referenceto FIG. 4, the first heat exchanger 401 can be coupled a vapor-liquidseparator 403, e.g., a flash drum, for the separation of the liquid andgas phases of the refrigerant. The vapor-liquid separator 403 can befurther coupled to a liquid pump 409, for pumping the separated liquidphase of the refrigerant.

In certain embodiments, the system 300 or 400 can include a second heatexchanger 304 or 404 for exchanging heat between a second process waterstream, e.g., transferred from the process plant system 302 or 402, andthe partially vaporized refrigerant. Examples of heat exchangers aredisclosed above. The second heat exchanger 304 can be coupled to themultiphase pump 303. Alternatively, and in reference to FIG. 4, thesecond heat exchanger 404 can be coupled to the liquid pump 409 for thetransfer of the liquid phase of the refrigerant from the vapor-liquidseparator 403 to the second heat exchanger 404. The liquid pump 409 canbe coupled to the second heat exchanger 404 via a transfer line 411. Thevapor-liquid separator 403 of system 400 can be coupled to a gascompressor 410 for compressing the separated vapor phase of therefrigerant. The gas compressor 410 can, in turn, be coupled to thesecond heat exchanger 404 for combining the compressed vapor phase ofthe refrigerant with the separated liquid phase to generate a partiallyvaporized refrigerant and to transfer the partially vaporizedrefrigerant to the second heat exchanger 404. The gas compressor 410 canbe coupled to the second heat exchanger 404 via the transfer line 411.

In certain embodiments, the second heat exchanger 304 or 404 can befurther coupled to the first heat exchanger 301 or 401. The second heatexchanger 304 or 404 can be coupled to the first heat exchanger 301 or401 through a liquid pump 308 or 408, e.g., for the transfer of thesecond process water stream from the second heat exchanger 304 or 404 tothe first heat exchanger 301 or 401. Non-limiting examples of liquidpumps for use in the present disclosure include peristaltic pumps,pneumatic pumps, diaphragm pumps, piston pumps, rotary pumps,centrifugal pumps, positive displacement pumps and reciprocating pumps.

The system 300 or 400 can further include a first expansion valve 305 or405 for lowering the temperature of the partially vaporized refrigerant.Expansion valves can change the temperature of a medium, e.g., arefrigerant, by altering the pressure. The pressure within the firstexpansion valve 305 or 405 can be in a range from about 4 bar to about 5bar. The first expansion valve 305 or 405 can be coupled to the secondheat exchanger 304 or 404.

The system 300 or 400 can further include a vapor-liquid separator,e.g., a flash drum, 306 or 406 for separating the liquid and vaporphases of the refrigerant. In certain embodiments, the vapor-liquidseparator 306 or 406 can be coupled to the first expansion valve 305 or405. In certain embodiments, and in reference to FIG. 3, thevapor-liquid separator 306 can be coupled to the multiphase pump 303 fortransferring at least a portion of the separated vapor phase of therefrigerant to the multiphase pump 303. Alternatively or additionally,and in reference to FIG. 4, the vapor-liquid separator 406 can becoupled to the gas compressor 410, e.g., for the transfer of at least aportion of the separated vapor phase to the gas compressor 410.

The system 300 or 400 can include a second expansion valve 307 or 407for lowering the temperature of the liquid phase of the refrigerant. Thesecond expansion valve 307 or 407 can be coupled to the vapor-liquidseparator 306 or 406. The second expansion valve 307 or 407 can also becoupled to the first heat exchanger 301 or 401 for the transfer of therefrigerant to the first heat exchanger 301 or 401, to exchange heatwith the first process water stream.

The following example is illustrative of the presently disclosed subjectmatter and should not be considered as a limitation in any way.

Example 1

A simulation using the software PRO/II (Invensys Systems, Inc.) wasperformed to demonstrate a method for cooling process plant wateraccording to one non-limiting embodiment of the disclosed subject matter(FIG. 3). In method simulation software such as, for example, PRO/II,each process component (e.g., flash drum, heat exchanger, etc.) of auser-specified process design/system is mathematically modeled includingby each piece of equipment, effluent streams, and attributes of chemicalcomponents. Interconnections and the interaction between components arealso integral to the model. Table 1 shows the changes in thetemperature, pressure and vapor fraction of the process plant water andrefrigerant during the simulation.

The simulated method included the use of a liquid refrigerant having atemperature of 9° C. to cool down a process water stream from atemperature of 38° C. to a chilled water temperature of 25° C. in afirst heat exchanger (HX1). In this Example, the refrigerant R134A wasused in the simulation. The refrigerant exiting the heat exchanger had atemperature of 6.7° C. with a vapor phase fraction of 40%. Therefrigerant was then combined with a vapor stream coming from a flashdrum further downstream and the refrigerant was fed to a multiphase pumpwhere the pressure of the refrigerant was raised from 3.7 bar to 13.9bar. The heat generated from the pump increased the refrigeranttemperature from an inlet temperature of 7.4° C. to an outlettemperature of 52.1° C. with a vapor fraction of 54.4% (Table 1).

The cooled process water was transferred to a plant process where itcooled down different streams in the plant with a total duty of 25.8 MWand exited the plant with an outlet water temperature of 31.1° C. Therefrigerant was then fed to a second heat exchanger (HX2) where it iscooled down against the process water exiting the plant. The temperatureof the process water increased from 31.1° C. to 38° C. and therefrigerant cooled to 51.5° C. with vapor fraction of 41%. The processwater was then pumped back to the first heat exchanger (HX1). Therefrigerant was then cooled by lowering its pressure in an expansionvalve (EV1) to 4.3 bar, where its temperature decreased to 11.2° C. Thevapor was then separated from the liquid by a flash drum and wascombined with the multiphase pump inlet feed mixture. The liquid streamwas fed to a second expansion valve (EV2) where its pressure was loweredto 4 bar forming a mixture with 1.5% gas fraction with a temperature of9° C. The mixture was recycled back to the first heat exchanger. Theliquid in the mixture to the multiphase pump had a viscosity of 0.25centipoise (cP), which is within the operating specification of themultiphase pumps.

TABLE 1 Flow rate Pressure Temperature Vapor Stream (t/h) (bar) (° C.)fraction (%) Inlet process water to HX1 3434.66 5.00 38.00 0.0 Outletprocess water from HX1 3434.66 4.50 25.03 0.0 Inlet refrigerant to HX12713.41 4.00 9.04 1.5 Outlet refrigerant from HX1 2713.41 3.70 6.74 40.0Inlet refrigerant to multiphase 4899.97 3.70 6.74 66.8 pump Outletrefrigerant from multiphase 4899.97 13.90 52.14 54.4 pump Outletrefrigerant from HX2 4899.97 13.70 51.56 41.1 Inlet process water to HX23434.66 4.47 31.12 0.0 Outlet refrigerant from EV1 4899.97 4.30 11.2144.8

In addition to the various embodiments depicted and claimed, thedisclosed subject matter is also directed to other embodiments havingother combinations of the features disclosed and claimed herein. Assuch, the particular features presented herein can be combined with eachother in other manners within the scope of the disclosed subject mattersuch that the disclosed subject matter includes any suitable combinationof the features disclosed herein. The foregoing description of specificembodiments of the disclosed subject matter has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosed subject matter to those embodimentsdisclosed. It will be apparent to those skilled in the art that variousmodifications and variations can be made in the compositions and methodsof the disclosed subject matter without departing from the spirit orscope of the disclosed subject matter. Thus, it is intended that thedisclosed subject matter include modifications and variations that arewithin the scope of the appended claims and their equivalents.

1. A method for cooling process plant water, the method comprising: (a)exchanging heat between a first process water stream and a liquidrefrigerant to lower the temperature of the process water stream,thereby generating a partially vaporized refrigerant that comprises avapor phase and a liquid phase; (b) increasing the pressure and/ortemperature of the partially vaporized refrigerant to generate apressurized partially vaporized refrigerant; (c) exchanging heat betweena second process water stream and the pressurized partially vaporizedrefrigerant to lower the temperature of the pressurized partiallyvaporized refrigerant and/or increase the temperature of the secondprocess water stream; (d) lowering the pressure and/or temperature ofthe pressurized partially vaporized refrigerant and separating out atleast a portion of the liquid phase from the partially vaporizedrefrigerant to generate a liquid refrigerant; and (e) lowering thetemperature of the liquid refrigerant to generate a cooled liquidrefrigerant suitable for exchanging heat with the first process waterstream.
 2. The method of claim 1, wherein the lowering the pressureand/or temperature of the partially vaporized refrigerant portion ofstep (d) occurs in a first expansion valve.
 3. The method of claim 1,wherein the lowering the temperature of the liquid refrigerant of step(e) occurs within a second expansion valve.
 4. The method of claim 1,wherein the liquid refrigerant comprises a refrigerant having aviscosity greater than or equal to about 0.1 cP at a temperature ofabout 0° C.
 5. The method of claim 1, wherein the liquid refrigerantcomprises a refrigerant having a boiling point temperature from about−10° C. to about −50° C.
 6. The method of claim 1, wherein the liquidrefrigerant comprises a refrigerant selected from the group consistingof R134A, R404A, R407C, R125, and R410A.
 7. The method of claim 1,wherein the partially vaporized refrigerant comprises a refrigeranthaving a vapor phase of about 30% to about 50%.
 8. The method of claim1, wherein the increasing the pressure and/or temperature of thepartially vaporized refrigerant occurs within a multiphase pump.
 9. Themethod of claim 1, further comprising transferring the cooled processwater to one or more process plants.
 10. The method of claim 1, wherein:step (a) further comprises exchanging heat between the first processwater stream and the liquid refrigerant within a first heat exchanger tolower the temperature of the first process water stream, therebygenerating the partially vaporized refrigerant, which comprises thevapor phase and the liquid phase, upon the exchange of heat with thefirst process water stream; step (b) further comprises increasing thepressure of the partially vaporized refrigerant and transferring atleast a portion of the partially vaporized refrigerant to a second heatexchanger; step (c) further comprises exchanging heat between a secondprocess water stream and the partially vaporized refrigerant portionwithin the second heat exchanger to decrease the temperature of therefrigerant; step (d) further comprises lowering the pressure and/ortemperature of the partially vaporized refrigerant portion andtransferring the partially vaporized refrigerant portion to avapor-liquid separator to separate the liquid phase from the vapor phasethereof, thereby generating the liquid refrigerant; and step (e) furthercomprises lowering the temperature of the liquid refrigerant andtransferring at least a portion of the refrigerant to the first heatexchanger to exchange heat with the first process water stream.
 11. Themethod of claim 10, wherein the increasing pressure of the partiallyvaporized refrigerant of step (b) occurs in a multiphase pump.
 12. Themethod of claim 10, further comprising: (f) transferring at least aportion of the vapor phase of the refrigerant from the separator to themultiphase pump.
 13. The method of claim 10, wherein the vapor-liquidseparator comprises a flash drum.
 14. A method for cooling process plantwater, the method comprising: (a) exchanging heat between a firstprocess water stream and a liquid refrigerant within a first heatexchanger to lower the temperature of the process water stream, therebypartially vaporizing the refrigerant upon the exchange of heat with thefirst process water stream; (b) transferring the first process waterfrom the first heat exchanger to one or more process plants; (c)transferring the partially vaporized refrigerant from the first heatexchanger to a multiphase pump to increase the pressure of the partiallyvaporized refrigerant; (d) transferring the partially vaporizedrefrigerant from the multiphase pump to a second heat exchanger; (e)exchanging heat between a second process water stream and the partiallyvaporized refrigerant within the second heat exchanger to decrease thetemperature of the refrigerant; (f) transferring the second processwater stream from the second heat exchanger to become the first processwater stream entering the first heat exchanger; (g) transferring thepartially vaporized refrigerant from the second heat exchanger to afirst expansion valve to lower the pressure and/or temperature of therefrigerant; (h) transferring the partially vaporized refrigerant fromthe first expansion valve to a vapor-liquid separator to separate theliquid phase from the vapor phase thereof, thereby generating a liquidrefrigerant; (i) transferring the liquid refrigerant from thevapor-liquid separator to a second expansion valve to lower thetemperature of the liquid refrigerant; and (j) transferring therefrigerant from the second expansion valve to the first heat exchangerto exchange heat with the first process water stream.
 15. A system forexchanging heat between a first process water stream and a secondprocess water stream with a refrigerant, the system comprising: (a) afirst heat exchanger for exchanging heat between the first process waterstream and the refrigerant and thereby generate a partially vaporizedrefrigerant having liquid and vapor phases; (b) a multiphase pump,coupled to the first heat exchanger, to increase the partially vaporizedrefrigerant pressure; (c) a second heat exchanger, coupled to themultiphase pump and the first heat exchanger, for exchanging heatbetween the second process water stream and the partially vaporizedrefrigerant; (d) a first expansion valve, coupled to the second heatexchanger, for lowering the lowering the pressure and/or temperature ofthe partially vaporized refrigerant temperature; (e) a vapor-liquidseparator, coupled to the first expansion valve and the multiphase pump,for separating the liquid and the vapor phases of the partiallyvaporized refrigerant; and (f) a second expansion valve, coupled to thevapor-liquid separator and the first heat exchanger, for lowering theliquid phase temperature of the refrigerant.
 16. The system of claim 15,wherein the vapor-liquid separator comprises a flash drum.
 17. Themethod of claim 7, wherein the lowering the pressure and/or temperatureof the partially vaporized refrigerant portion of step (d) occurs in afirst expansion valve.
 18. The method of claim 4, wherein the loweringthe pressure and/or temperature of the partially vaporized refrigerantportion of step (d) occurs in a first expansion valve.
 19. The method ofclaim 5, wherein the lowering the pressure and/or temperature of thepartially vaporized refrigerant portion of step (d) occurs in a firstexpansion valve.
 20. The method of claim 6, wherein the lowering thepressure and/or temperature of the partially vaporized refrigerantportion of step (d) occurs in a first expansion valve.